On drilling rigs, drill pipe is raised from the ground to the rig floor, and conversely lowered from the rig floor to the ground by means of a catwalk and slide. A catwalk typically consists of a long, rectangular platform usually made of steel that is located at the bottom of the slide and oriented perpendicularly to the V-door. The catwalk platform is used as a staging area for drill pipe that is about to be lifted to the rig floor, or which has been lowered from the rig floor. The slide is an inclined plane below the V-door that connects the rig floor to the catwalk. It is frequently a reinforced steel plate with a central groove, which acts as a guide when pipes are dragged or pushed to and from the rig floor.
There are a number of mechanized systems designed to lift or push drill pipe along the catwalk to the slide and up to the V-door. A commonly used conventional system uses a skate that pushes the pipe along the catwalk and up the inclined slide. However, the skate delivers the drill pipe to the rig floor in an uncontrolled and projectile-like manner posing a safety risk to those working in proximity to the V-door. Furthermore, a significant amount of force is required to overcome frictional and gravitational forces when the drill pipe is pushed up the slide in the conventional system. Also, the steepness of the slide in the conventional system poses a significant risk when used for access by workers. Conventional delivery systems are also restricted to the delivery of drill pipe and occasionally, lighter rig equipment such as slips. Further still, many conventional systems can deliver only one drill pipe per delivery cycle.
What is needed is an apparatus for delivering a drill pipe between the ground and a rig floor that mitigates the limitations of a conventional catwalk and slide system.